In recent years, a highly safe and high-capacity lithium ion battery has been actively developed.
Due to the liquid electrolyte, a lithium ion battery which has been practically used at present has a drawback that it is not safe. Therefore, an inorganic solid electrolyte has been developed (Patent Document 1).
All-solid lithium battery using an inorganic solid electrolyte in Patent Document 1 is highly safe. However, since it is produced by subjecting lithium sulfate and phosphorous pentasulfide to mechanical milling, the surface is not uniform, and hence, the battery performance may be deteriorated.
The uniformity of the electrolyte surface is an important property in stabilizing the performance of a battery as a final product. Since the electrolyte surface is a medium on which lithium ions move directly, if the uniformity thereof is poor, resistance partially increases, and as a result, stable battery performance is not developed. Further, in order to allow it to be glass ceramic, if the electrolyte surface is not uniform, crystals that are favorable for attaining excellent conductivity are not formed partially. As a result, when used in a battery, such an un-uniform surface of an electrolyte may lower the battery performance.